1. Technical Field
The present invention relates to an electro-optical device, an electronic apparatus, and a contact detection method for detecting the touching of an object such as a finger, a pen, or the like on a screen.
2. Related Art
A liquid crystal display device that has a touch-screen function is described in JP-T-2007-510949. The related-art liquid crystal display device that is described in JP-T-2007-510949 judges whether a screen is touched or not by detecting a change in the capacitance value of a capacitive element, which is made up of two electrodes that are respectively provided on two substrates arrayed opposite to each other and liquid crystal that is sandwiched between these electrodes.
In the operation of a liquid crystal display device, an alternating voltage is applied to liquid crystal in order to prevent the occurrence of image quality degradation such as a burn-in problem or the like. For example, a data electric potential that is applied to a pixel electrode, that is, the level of a data voltage that is applied to a pixel electrode, is alternated between a high level that is applied during a high electric potential period and a low level that is applied during a low electric potential period repeatedly whereas a common electric potential Vcom that is applied to a common electrode is taken as a reference. When liquid crystal is AC driven with an alternating level shift as explained above, the capacitance value of a capacitive element changes when it is not supposed to due to variations in the common electric potential Vcom as the level of the common voltage Vcom varies during the AC driving of the liquid crystal. In such a case, the accuracy of touch detection decreases because it is affected by the change in the capacitance value of the capacitive element due to the change in the level of the common voltage Vcom.